1. Field of the Invention
The present invention relates to a photograph processing device and more particularly, to a printer processor which has the functions of measuring the density of an image recorded on a light-sensitive material and correcting exposure conditions in accordance with the image density measured, and automatically performs operations, such as printing and developing.
2. Description of the Related Art
To always finish color prints with good quality in printer processors, a developing operation must be performed properly and exposure conditions for a printing section must be set accurately. In view of the foregoing, standard exposure conditions are set at the time of installing the printer processor. However, exposure conditions must be corrected and re-set when color paper with a different emulsion number is used, a printer lamp is changed, developing solution is changed, the number of colors contained in a photograph increases or decreases with the turning of the seasons, or at similar events. To correct the exposure conditions, a reference negative film is prepared with including negative frames containing the image of a gray object. The gray object on the negative film is photographed on color paper which is printed and subjected to developing, fixing, washing and drying operations, thereby producing a test print. The reference density of a previously-printed/developed reference print and the image density of the foregoing test print are measured using a densitometer. They are then compared to derive correction values by which the exposure conditions are set.
The principle of correction will be described with reference to a set of simplified exposure calculation expressions (1) as below. However, C, M and Y designate primary colors (subtractive). ##EQU1## where D.sub.CO,D.sub.MO,D.sub.YO : the density for exposure control, for a paper channel,
D.sub.C,D.sub.M,D.sub.Y : the integral transmission density (LATD) measured value of a negative frame to be printed, PA1 I.sub.C,I.sub.M,I.sub.Y : the number of color key stages (0 for no correction), PA1 I.sub.D : the number of density key stages (0 for no correction), PA1 K.sub.C,K.sub.M,K.sub.Y : the value of color key step, PA1 K.sub.D : the value of density key step, PA1 B.sub.PC,B.sub.PM,B.sub.PY : paper balance value (0 for a reference value). PA1 B.sub.NC,B.sub.NM,B.sub.NY : negative-type balance value (0 for a reference), PA1 D.sub.NC,D.sub.NM,D.sub.NY : the density of a reference negative frame (normal) of the above-mentioned negative type, PA1 C.sub.C,C.sub.M,C.sub.Y : the value of slope (this has a different value depending on "O" or "U" as follows:
for a constant paper channel,
C.sub.CO,C.sub.MO,C.sub.YO : the value of overslope of the above-mentioned negative type, PA2 C.sub.CU,C.sub.MU,C.sub.YU : the value of underslope of the above-mentioned megative type).
The amount of exposure E.sub.R for red (R), for example, is determined by EQU E.sub.R =E.sub.N .multidot.10.sup.CO.spsp.D ( 2)
where E.sub.N is the constant or amount of exposure of the reference negative frame (normal) of the above-mentioned negative type. Similarly, the amount of exposures for green (G) and blue (B) are determined by D.sub.MO and D.sub.YO, respectively.
Letting .DELTA.D.sub.PC be a minute density change of cyan of the color paper and .gamma..sub.C be the value of .gamma., there is the following expression: EQU .DELTA.D.sub.PC =.gamma.C.multidot..DELTA.log(E.sub.R) (3)
and from the expressions (2) and (3), the following expression (4) is obtained: EQU .DELTA.D.sub.PC =.gamma.C.multidot..DELTA.D.sub.CO .multidot.log(E.sub.N)(4)
From this (4), .DELTA.D.sub.CO can be calculated backward.
Letting .DELTA.D.sub.PC, .DELTA.D.sub.PM, .DELTA.D.sub.PY be the difference between the denisty of the normal test print of the reference negative type and the density of the reference print, if the result of calculation D.sub.CO of the expression (1) is set as below: EQU D.sub.CO '=D.sub.CO -.DELTA.D.sub.CO ( 5)
the difference .DELTA.D.sub.PC can be made zero by changing a certain constant which depends on what density the reference negative frame has. Similarly to the expression (5), the following are defined: EQU D.sub.MO '=D.sub.MO -.DELTA.D.sub.MO ( 6) EQU D.sub.YO '=D.sub.YO -.DELTA.D.sub.YO ( 7)
Condition settings are made as follows.
1 In the case of a normal negative
The measured density D.sub.C,D.sub.M,D.sub.Y of the normal negative frame is stored in D.sub.NC,D.sub.NM,D.sub.NY of the negative type channel.
A normal negative print is produced, and the correction value .DELTA.D.sub.CO,.DELTA.D.sub.MO,.DELTA.D.sub.YO is obtained in accordance with the expression (5), (6), (7) from the difference between the density of the reference print and the density of the normal negative print, and is stored in B.sub.NC,B.sub.NM,B.sub.NY of the negative type channel.
2 In the case of over negative (performed after Item 1 above)
An over negative print is produced, the value D.sub.CO ',D.sub.MO ',D.sub.YO ' is obtained in accordance with the expression (5), (6), (7) from the difference between the density of the over negative print and the density of the reference print. The value of overslope C.sub.CO,C.sub.MO,C.sub.YO which makes the result of the calculation D.sub.CO,D.sub.MO,D.sub.YO of the expression (1) equal to the foregoing value is calculated backward, and stored in C.sub.CO,C.sub.MO,C.sub.YO of the negative type channel.
3 In the case of under negative (performed after Item 1)
Similar to Item 2, the value C.sub.CU,C.sub.MU,C.sub.YU is obtained and stored in C.sub.CU,C.sub.MU,C.sub.YU of the negative type channel. In the prior art, the density in the item 1, 2, 3 was manually measured and the related negative type channel was manually designated. The constants for the negative channel are listed in the following table.
TABLE ______________________________________ nega. type 1 nega. type 2 nega. type 3 . . . ______________________________________ B B.sub.NC B.sub.NM B.sub.NY B.sub.NC B.sub.NM B.sub.NY B.sub.NC B.sub.NM B.sub.NY . . . N D.sub.NC D.sub.NM D.sub.NY D.sub.NC D.sub.NM D.sub.NY D.sub.NC D.sub.NM DNY . . . O C.sub.CO C.sub.MO C.sub.YO C.sub.CO C.sub.MO C.sub.YO C.sub.CO C.sub.MO C.sub.YO . . . U C.sub.CU C.sub.MU C.sub.YU C.sub.CU C.sub.MU C.sub.YU C.sub.CU C.sub.MU C.sub.YU . . . ______________________________________
In conventional printer processors, the drying operation is attained by exposing the test print to high-temperature air; thus, the temperature of the dried test print is as high as about 90.degree. C. at the time of density measurement. It is known that the image density of the print varies with temperature, especially, the density of cyan varies largely with temperature, and the cyan density of the print at about 90.degree. C. is smaller by about 5% than that at room temperature. Therefore, the image density of the test print immediately after drying differs from that at room temperature. Thus, if correction values for the exposure conditions are calculated on the basis of the image density of the test print immediately after drying, optimal exposure conditions at room temperature cannot be obtained.